This application claims the benefit of a Japanese Patent Application No. 2001-163256 filed May 30, 2001, in the Japanese Patent Office, the disclosure of which is hereby incorporated by reference.
1. Field of the Invention
The present invention generally relates to reproducing methods and storage apparatuses, and more particularly to a reproducing method for reproducing information from a recording medium such as a magneto-optical disk, and to a storage apparatus which employs such a reproducing method.
2. Description of the Related Art
Of various magneto-optical disk units, there is a magneto-optical disk unit which reproduces information from a magneto-optical disk employing Magnetic Super Resolution (MSR), by a so-called double mask Rear Aperture Detection (RAD). The magneto-optical disk employing MSR will hereinafter simply be referred to as a MSR disk. According to the double mask RAD, heat and magnetic field applied on the MSR disk are controlled to eliminate interference of information recorded before and after along a track direction, so as to improve the recording density.
In each zone on the MSR disk other than a control zone in which control information is recorded as variations in geometrical configuration such as pits, information is recorded with a recording format which includes a header and a recording field. The header includes a sector mark which indicates a start of a sector, a VFO field for PLL phase synchronization and AGC, an address mark for synchronizing to a following ID portion, the ID portion which includes information for recognizing a sector address, and the like. The header is recorded as variations in geometrical configuration such as concave or convex pits. On the other hand, the recording field includes a gap portion which indicates a start of the recording field, a VFO field for PLL phase synchronization and AGC, a synchronizing portion for synchronizing to data, a data field for recording data, and the like. The recording field is recorded magneto-optically.
According to a conventional magneto-optical disk unit, when the reproduction of the ID portion of the header ends, a power (hereinafter referred to as an LD power) of a light beam which is emitted from a light source such as a laser diode (LD) and is irradiated on the MSR disk is increased to an LD power which is capable of reproducing the data field of the recording field, and the reproduction is continued at the increased LD power, as shown in FIG. 1. In FIG. 1, (a) indicates the LD power, and (b) indicates the ID portion of the header and the data field of the recording field in the zone.
However, a hysteresis relationship shown in FIG. 2 exists between the mask and the heat which is required to form the mask. In FIG. 2, the ordinate indicates a region where the mask is formed and a region where no mask is formed, and the abscissa indicates the LD power at the time of the reproduction. For this reason, the present inventors have newly discovered that the LD power which is required to reproduce the data of the data field at the start of the reproduction is higher than the LD power which is required to continue reproducing the data of the data field.
In other words, although the LD power immediately after the reproduction of the data of the data field is started may be lower than the LD power which is required to reproduce the data of the data field at the start of the reproduction, the conventional magneto-optical disk unit continues to reproduce the data of the data field using the high LD power. Consequently, the present inventors have newly discovered that a range of the LD power in which the reproduction can be carried out is small, that is, a margin of the LD power at the time of the reproduction is small.
Accordingly, it is a general object of the present invention to provide a novel and useful reproducing method and storage apparatus, in which the problems described above are eliminated.
Another and more specific object of the present invention is to provide a reproducing method and a storage apparatus which can realize a high-density recording and reproduction by increasing the margin of the LD power at the time of the reproduction.
Still another object of the present invention is to provide a reproducing method which uses a light beam to reproduce information from a recording medium having an information region with a recording format which includes a header including position information and a recording field including a data field for recording data, comprising the step of (a) controlling a power L2 of the light beam in a vicinity of a start of the recording field to become higher than a power L3 at the data field of the recording field. According to the reproducing method of the present invention, it is possible to realize a high-density recording and reproduction by increasing the margin of the power of the light beam at the time of the reproduction, and make it possible to realize a highly reliable reproducing method which can sufficiently reproduce information even when the power slightly deviates from an optimum value due to effects of environmental changes or the like.
A further object of the present invention is to provide a storage apparatus which uses a light beam to reproduce information from a recording medium having an information region with a recording format which includes a header including position information and a recording field including a data field for recording data, comprising a light source for emitting the light beam, and control means for controlling a power L2 of the light beam in a vicinity of a start of the recording field to become higher than a power L3 at the data field of the recording field. According to the storage apparatus of the present invention, it is possible to realize a high-density recording and reproduction by increasing the margin of the power of the light beam at the time of the reproduction, and make it possible to realize a highly reliable storage apparatus which can sufficiently reproduce information even when the power slightly deviates from an optimum value due to effects of environmental changes or the like.